On Fri, Sep 12, 2014 at 10:10:52AM +0900, Kamezawa Hiroyuki wrote: > (2014/09/12 0:41), Vladimir Davydov wrote: > > In the next patch I need a quick way to get a value of > > MEM_CGROUP_STAT_RSS. The current procedure (mem_cgroup_read_stat) is > > slow (iterates over all cpus) and may sleep (uses get/put_online_cpus), > > so it's a no-go. > > > > This patch converts memory cgroup statistics to use percpu_counter so > > that percpu_counter_read will do the trick. > > > > Signed-off-by: Vladimir Davydov <[email protected]> > > > I have no strong objections but you need performance comparison to go with > this. > > I thought percpu counter was messy to be used for "array". > I can't understand why you started from fixing future performance problem > before > merging new feature.
Because the present implementation of mem_cgroup_read_stat may sleep (get/put_online_cpus) while I need to call it from atomic context in the next patch. I didn't do any performance comparisons, because it's just an RFC. It exists only to attract attention to the problem. Using percpu counters was the quickest way to implement a draft version, that's why I chose them. It may have performance impact though, so it shouldn't be merged w/o performance analysis. Thanks, Vladimir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
